WO2011065137A1 - Élément électroluminescent organique, son procédé de fabrication et dispositif d'affichage par électroluminescence organique - Google Patents

Élément électroluminescent organique, son procédé de fabrication et dispositif d'affichage par électroluminescence organique Download PDF

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WO2011065137A1
WO2011065137A1 PCT/JP2010/067883 JP2010067883W WO2011065137A1 WO 2011065137 A1 WO2011065137 A1 WO 2011065137A1 JP 2010067883 W JP2010067883 W JP 2010067883W WO 2011065137 A1 WO2011065137 A1 WO 2011065137A1
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light emitting
organic
host material
layer
emitting layer
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PCT/JP2010/067883
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Japanese (ja)
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岡本　健
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シャープ株式会社
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Priority to US13/511,636 priority Critical patent/US8860013B2/en
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/10—Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
    • H10K2101/10—Triplet emission
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
    • H10K2101/40—Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
    • H10K2101/90—Multiple hosts in the emissive layer

Definitions

  • the present invention relates to an organic electroluminescence element that realizes high luminance, high efficiency, and a long lifetime, a method for manufacturing the same, and an organic electroluminescence display device.
  • FPD thin flat panel display
  • LCD liquid crystal display
  • PDP self-luminous plasma display panel
  • inorganic electroluminescence (inorganic EL) display or organic electroluminescence (organic EL).
  • a display or the like is known.
  • organic EL displays are actively researched and developed because the elements used for display (organic EL elements) are thin and lightweight, and have characteristics such as low voltage drive, high luminance, and self-luminous emission. Has been done.
  • the organic EL element has a pair of electrodes (anode and cathode) on a substrate, and an organic layer having at least a light emitting layer between the pair of electrodes.
  • the light emitting layer is formed by doping a host material with an organic light emitting material.
  • a hole injection layer doped with an acceptor in the host material is provided between the light emitting layer and the anode, and an electron injection layer doped with a donor in the host material is provided between the light emitting layer and the cathode.
  • the organic EL element In the organic EL element, by applying a voltage to the anode and the cathode, holes are injected from the anode into the organic layer, and electrons are injected from the cathode into the organic layer. Holes and electrons injected from both electrodes recombine in the light emitting layer to generate excitons.
  • the organic EL element emits light using light emitted when the exciton is deactivated.
  • an organic light emitting material such as a phosphorescent light emitting material or a fluorescent light emitting material is generally used.
  • An organic EL element using a phosphorescent material has advantages of high luminous efficiency and a long emission lifetime, and in particular, recently, an organic EL element using a phosphorescent material in a light emitting layer is becoming widespread.
  • development of organic EL elements in which a phosphorescent material having an internal quantum yield of 100% at the maximum is introduced is progressing.
  • a phosphorescent material having an internal quantum yield of 100% at the maximum is introduced into the organic EL element that emits red light and the organic EL element that emits green light.
  • organic EL elements that emit blue light phosphorescent light emitting materials having an internal quantum yield of 100% at the maximum have not been introduced, and fluorescent light emitting materials having an internal quantum yield of 25% at the maximum have been used.
  • blue light emission requires higher energy than red light emission and green light emission. Furthermore, when the energy is obtained from the excited triplet level (T 1 ), it is necessary to confine all of T 1 , electrons, and holes in the phosphorescent material in the light emitting layer. Therefore, the gap between the highest occupied level (HOMO level) and the lowest vacant level (LUMO level) is made very large including not only the material constituting the light emitting layer but also the material around the light emitting layer. There is a need.
  • a host material constituting the light-emitting layer is a material that is conjugated between molecules, exhibits an interaction, and has high carrier mobility. Is difficult. Therefore, when a blue phosphorescent material is used, a high voltage is required for driving, but the luminous efficiency is low.
  • FIG. 8 shows a specific example of a conventional organic EL element 31 using a blue phosphorescent material.
  • FIG. 8 is a diagram showing an energy diagram of each layer constituting a conventional organic EL element 31 using a blue phosphorescent material.
  • UGH2 since UGH2 has a wide gap, holes cannot be efficiently propagated from the hole transport layer 34 to the light emitting layer 35. Similarly, electrons cannot be efficiently propagated from the electron transport layer 36 to the light emitting layer 35. Therefore, as described above, the organic EL element 31 using the blue phosphorescent material as described above requires a high voltage for driving, but has a problem that the luminous efficiency is low.
  • Non-Patent Document 1 discloses an organic EL element in which two light emitting layers are provided. Specifically, an organic EL device including an organic layer in which a hole injection layer, a first light emitting layer, a second light emitting layer, and an electron injection layer are formed in this order between a pair of electrodes is disclosed.
  • an organic EL element having a small gap between the HOMO level and the LUMO level in the first light emitting layer and the second light emitting layer can be obtained. Therefore, a host material that improves the mobility of holes and electrons in the light-emitting layer may be used. This is because holes and electrons are transported by hopping conduction in the organic vapor-deposited film (Non-Patent Document 2). In order for electrons to conduct by hopping between molecules, the overlap of wave functions between the electronic state of the neutral state and the radical anion state must be large. On the other hand, in the hole, in order to conduct by hopping between molecules, it is necessary that the wave function overlap between the electronic state of the neutral state and the radical cation state is large.
  • the organic EL element disclosed in Non-Patent Document 1 when electrons are propagated from the electron injection layer to the second light emitting layer, the electrons are propagated to the light emitting dopant (FIrpic).
  • the organic EL element disclosed in this document has a configuration in which electrons are easily propagated from the light emitting dopant to the first light emitting layer. Therefore, according to this configuration, holes and electrons do not recombine at the interface between the first light emitting layer and the second light emitting layer, and the probability of recombination decreases. That is, an internal quantum yield will fall.
  • Non-Patent Document 1 FIrpic that emits sky blue is used as the phosphorescent material of the first light emitting layer and the second light emitting layer. Since the gap between the HOMO level and the LUMO level of the FIrpic is small, an organic EL element with a low driving voltage and high luminous efficiency can be obtained. Therefore, when a phosphorescent material that emits deep blue light is used, the gap between the HOMO level and the LUMO level of such a phosphorescent material is large. Therefore, the host having a large gap between the HOMO level and the LUMO level. Material is required. Therefore, although a high voltage is required for driving, the problem that the light emission efficiency becomes low for that is still left.
  • the present invention has been made in view of the above problems, and an object thereof is to provide an organic EL element that can be driven at a low voltage and has high luminous efficiency, and a method for manufacturing the same.
  • an organic electroluminescence device includes an anode and a cathode, and an organic layer formed between the anode and the cathode and having at least a light emitting layer on a substrate.
  • the light emitting layer is located on the anode side and is composed of a first light emitting layer made of a first host material that is a hole transporting host, and the electron emitting host is located on the cathode side.
  • the material, and the highest occupied level (HOMO) and the lowest empty level (LUMO) of each of the organic light-emitting materials satisfy the following relational expressions (1) and (2): To have.
  • the highest occupied level of the host material constituting the first light emitting layer is shallower than the highest occupied level of the organic light emitting material.
  • the probability of recombination of holes and electrons can be increased.
  • the lowest vacant level of the host material constituting the second light emitting layer is deeper than the lowest vacant level of the organic light emitting material.
  • the probability of recombination of holes and electrons can be increased.
  • the organic electroluminescence display device is characterized by comprising display means in which the above-described organic electroluminescence element is formed on a thin film transistor substrate in order to solve the above-mentioned problems.
  • the organic EL element having a low driving voltage and high luminous efficiency is provided, a display device with high luminance, high efficiency, and long life can be provided.
  • the manufacturing method of the organic electroluminescent element which concerns on this invention is the organic layer which has at least the light emitting layer formed between the anode and the cathode, and the said anode and the said cathode,
  • the method of manufacturing an organic electroluminescence device comprising a substrate, an anode forming step for forming the anode on the substrate, and a hole injection layer in which holes are injected from the anode are formed on the anode.
  • the first host material and the second host material are doped with the same organic light emitting material, and the following relational expression ( Using the first host material, the second host material, and the organic light emitting material each having the highest occupied level (HOMO) and the lowest vacant level (LUMO) satisfying 11) to (16) , Above It is characterized by forming a light layer and the second emitting layer.
  • the organic electroluminescence device it is possible to reduce the number of holes that move to the second light emitting layer without recombining with electrons, and to reduce the number of electrons that move to the first light emitting layer without recombining with holes. .
  • the probability that holes and electrons recombine can be increased, the drive voltage of the organic EL element can be lowered.
  • the probability of recombination of holes and electrons in the light emitting layer is increased, the internal quantum yield is improved, and the light emission efficiency can be improved.
  • the organic electroluminescence element (organic EL element) is configured by laminating a pair of electrodes (anode and cathode) and an organic layer including a light emitting layer between a pair of electrodes on a substrate. Is done. A more specific configuration will be described below with reference to FIG. FIG. 2 is a view showing a cross section of the organic EL element 11.
  • a plurality of thin film transistors each including a gate electrode 43, a drain electrode 44, a source electrode 45, and a gate insulating film 46 are formed on an insulating substrate 41 at a predetermined interval.
  • a connection wiring 47 is formed from the insulating substrate 41 to the TFT.
  • a planarizing film 81 is disposed on each TFT, and a contact hole 48 is formed in the planarizing film 81.
  • the drain electrode 44 of the TFT is electrically connected to the anode 12 through the contact hole 48.
  • An edge cover 49 is provided between the adjacent anodes 12, and the hole injection layer 13, the hole transport layer 14, the light emitting layer 15, and the hole blocking are disposed at a position opposite to the TFT of the anode 12.
  • An organic layer composed of the layer 8, the electron transport layer 16, and the electron injection layer 17, and the cathode 9 are formed.
  • the top of the cathode 9 is covered with an inorganic sealing film 54, and the anode 12, the organic layer, and the cathode 9 are sealed with the inorganic sealing film 54.
  • a light absorption layer 50, a phosphor layer 51, and a scatterer layer 52 are formed on the insulating substrate 41 facing the insulating substrate 41 on which the TFT is formed.
  • a resin sealing film 53 is formed between the two insulating substrates 41.
  • the light emitting layer 15 of the organic EL element 11 according to the present embodiment has a two-layer structure, and includes a first light emitting layer and a second light emitting layer.
  • the organic EL device 11 according to the present embodiment is configured such that the gap between the highest occupied level (HOMO level) and the lowest vacant level (LUMO level) of the host material constituting the light emitting layer 15 is reduced. ing. Thereby, it is possible to increase the probability of recombination of holes and electrons in the light emitting layer 15 while maintaining high mobility of holes and electrons in the organic layer. This will be described in detail below.
  • FIG. 1 is a diagram showing an energy diagram of each layer constituting the organic EL element 11.
  • the organic layer of the organic EL element 11 is formed by sequentially forming the hole injection layer 13, the hole transport layer 14, the light emitting layer 15, the electron transport layer 16, and the electron injection layer 17.
  • the light emitting layer 15 has a two-layer structure, and includes a first light emitting layer 15a and a second light emitting layer 15b.
  • the first light emitting layer 15a and the second light emitting layer 15b are doped with a single phosphorescent material.
  • the first light emitting layer 15a is located on the anode 12 side, receives holes injected from the anode 12 from the hole transport layer 13, and propagates to the vicinity of the interface with the second light emitting layer 15b.
  • the second light emitting layer 15b is located on the cathode (not shown) side, receives electrons injected from the cathode from the electron transport layer 16, and propagates to the vicinity of the interface of the first light emitting layer 15a.
  • the holes propagated from the first light emitting layer 15a and the electrons propagated from the second light emitting layer 15b recombine, Emits light.
  • the organic EL element 11 is configured such that the holes propagated from the hole transport layer 13 do not move to the second light emitting layer 15b, and the electrons propagated from the electron transport layer 16 are the first.
  • the light emitting layer 15a is configured not to move.
  • the host material (first host material; hole transporting host material) constituting the first light emitting layer 15a includes the LUMO level 19 of the phosphorescent material and the second light emission.
  • a material (
  • the host material constituting the second light emitting layer 15b has a HOMO level 18 of the phosphorescent light emitting material and a HOMO level deeper than that of the host material constituting the first light emitting layer 15a (
  • ) material is used.
  • the HOMO level of the host material constituting the second light emitting layer 15b is deeper than the HOMO levels of the host material and phosphorescent light emitting material constituting the first light emitting layer 15a (
  • the holes propagated to the first light emitting layer 15a are the second light emitting layer. The movement to 15b can be blocked.
  • the LUMO level of the host material constituting the first light emitting layer 15a is shallower than the LUMO levels of the host material and phosphorescent light emitting material constituting the second light emitting layer 15b (
  • light is emitted by recombination of holes and electrons propagated to the phosphorescent material at the interface between the first light emitting layer 15a and the second light emitting layer 15b.
  • the light emitting layer 15 has a two-layer structure, and is used for the light emitting layer 15 in consideration of the HOMO level and the LUMO level of the phosphorescent light emitting material and the host material.
  • the host material is determined.
  • the electrons injected from the cathode can be prevented from moving to the first light emitting layer 15a. This makes it possible to reduce the number of holes that move to the second light emitting layer 15b without recombining with electrons, and to reduce the number of electrons that move to the first light emitting layer 15a without recombining with holes.
  • the probability that holes and electrons recombine can be increased. Therefore, in the organic EL element 11 according to the present embodiment, the probability that holes and electrons are recombined in the light emitting layer 15 can be increased, so that the internal quantum yield can be improved and the light emission efficiency can be improved.
  • the conventional organic EL element using a blue phosphorescent light emitting material has a problem that the light emitting efficiency is low for a high driving voltage.
  • a blue phosphorescent material even when a blue phosphorescent material is used, holes can be prevented from moving to the second light emitting layer 15b, and electrons can be prevented from moving to the first light emitting layer 15a. be able to. That is, since the probability that holes and electrons recombine can be increased, the internal quantum yield of the organic EL element 11 can be improved, and the light emission efficiency can be improved.
  • the organic EL element 11 includes a hole injection layer 13, a hole transport layer 14, a light emitting layer 15, and an electron transport layer between an anode 12 and a cathode formed on a substrate (not shown). 16 and an organic layer composed of an electron injection layer 17.
  • substrate which comprises the organic EL element 11 should just be a board
  • the material that can be used as the substrate of the organic EL element 11 is not particularly limited, and for example, a known insulating substrate material can be used.
  • an inorganic material substrate made of glass, quartz, or the like, or a plastic substrate made of polyethylene terephthalate, polyimide resin, or the like can be used.
  • a substrate in which an insulating material made of silicon oxide or an organic insulating material is coated on a surface of a metal substrate made of aluminum (Al) or iron (Fe) can be used.
  • substrate etc. which insulated the surface of the metal substrate which consists of Al etc. by methods, such as anodizing, can also be utilized.
  • a material that does not have optical transparency for the substrate For example, a semiconductor substrate such as a silicon wafer may be used.
  • a light-transmitting material for the substrate for example, a glass substrate or a plastic substrate may be used.
  • the electrodes constituting the organic EL element 11 may function as a pair like the anode 12 and the cathode. Each electrode may have a single layer structure made of one electrode material or a laminated structure made of a plurality of electrode materials.
  • the electrode material that can be used as the electrode of the organic EL element 11 is not particularly limited, and for example, a known electrode material can be used.
  • Examples of the anode 12 include metals such as gold (Au), platinum (Pt), and nickel (Ni), and transparent materials such as indium tin oxide (ITO), tin oxide (SnO 2 ), and indium zinc oxide (IZO). Electrode materials can be used.
  • metals such as gold (Au), platinum (Pt), and nickel (Ni)
  • transparent materials such as indium tin oxide (ITO), tin oxide (SnO 2 ), and indium zinc oxide (IZO). Electrode materials can be used.
  • the cathode metals such as lithium (Li), calcium (Ca), cerium (Ce), barium (Ba), aluminum (Al), or magnesium (Mg) containing these metals: silver (Ag) Alloys, alloys such as Li: Al alloys, and the like can be used.
  • an electrode material that transmits light for one electrode it is preferable to use an electrode material that transmits light for one electrode and an electrode material that does not transmit light for the other electrode.
  • an electrode material that does not transmit light a black electrode such as tantalum or carbon, a reflective metal electrode such as Al, Ag, Au, Al: Li alloy, Al: neodymium (Nd) alloy, or Al: silicon (Si) alloy Etc.
  • the organic layer has a hole injection layer 13, a hole transport layer 14, a light emitting layer 15, an electron transport layer 16, and an electron injection layer 17.
  • the light emitting layer 15 has a two-layer structure, and includes the first light emitting layer 15a and the second light emitting layer 15b. Each layer is doped with a single phosphorescent material.
  • the phosphorescent material that can be used for the light emitting layer 15 is not particularly limited, and for example, a known phosphorescent material can be used.
  • FIr6 iridium bis (4 ′, 6′-diflu
  • the host material constituting the first light emitting layer 15a includes a phosphorescent material and a LUMO shallower than the host material constituting the second light emitting layer 15b.
  • a material having a level is used. Therefore, the host material used for the second light emitting layer 15b in the first embodiment can be used as the host material constituting the first light emitting layer 15a. This can prevent electrons from moving to the first light emitting layer 15a.
  • the HOMO level of the host material constituting the first light emitting layer 15a is shallower than the HOMO level 18 of the phosphorescent light emitting material. Furthermore, the difference between the HOMO level of the host material constituting the first light emitting layer 15a and the HOMO level 18 of the phosphorescent light emitting material is preferably within 0.5 eV. This is related to the fact that the transport of holes and electrons in the organic EL element is performed by hopping conduction. When the difference between the level where holes are trapped and the level where holes are hopped is ⁇ E during hopping conduction, the hole mobility decreases by exp ( ⁇ E / RT) (R : Gas constant, T: Absolute temperature [K]).
  • the probability that holes are thermally excited increases.
  • the probability that holes and electrons recombine can be increased. This value can be explained by the Arrhenius equation.
  • the difference between the HOMO level of the host material constituting the first light emitting layer 15a and the HOMO level 18 of the phosphorescent light emitting material is within 0.5 eV, phosphorescence from the host material constituting the first light emitting layer 15a occurs. Hole transfer to the luminescent material occurs.
  • the gap between the HOMO level and the LUMO level of the host material itself is larger than 0 eV, the gap between the HOMO level and the LUMO level of the host material itself. It is possible to reduce the voltage of the device itself.
  • a host material having a T 1 larger than T 1 of the phosphorescent light emitting material used for the light emitting layer 15 for the first light emitting layer 15a it is preferable to use a host material having a T 1 larger than T 1 of the phosphorescent light emitting material used for the light emitting layer 15 for the first light emitting layer 15a. Even when the host material has T 1 smaller than T 1 of the phosphorescent material, if the difference is about 0.1 eV, transfer of excitation energy from the phosphorescent material hardly occurs. Therefore, any host material having a T 1 smaller by about 0.1 eV than the T 1 of the phosphorescent material can be applied.
  • the second light emitting layer 15b will be described.
  • the phosphorescent material and the first light-emitting layer 15a are configured as the host material constituting the second light-emitting layer 15b so that holes do not move from the first light-emitting layer 15a to the second light-emitting layer 15b.
  • a material having a HOMO level deeper than that of the host material is used. Therefore, the host material used for the first light emitting layer 15a in the first embodiment can be used as the host material constituting the second light emitting layer 15b. This can prevent holes from moving to the second light emitting layer 15b.
  • the LUMO level of the host material constituting the second light emitting layer 15b is preferably deeper than the LUMO level 19 of the phosphorescent light emitting material. Furthermore, the difference between the LUMO level of the host material constituting the second light emitting layer 15b and the LUMO level 19 of the phosphorescent light emitting material is preferably within 0.5 eV.
  • This value is obtained by applying an electric field in the same manner as the energy difference shown in the difference between the HOMO level of the host material constituting the first light emitting layer 15a and the HOMO level 18 of the phosphorescent light emitting material. Electrons hardly move from the host material constituting the second light emitting layer 15b to the cathode side material. In other words, when the difference between the LUMO level of the host material constituting the second light emitting layer 15b and the LUMO level 19 of the phosphorescent light emitting material is within 0.5 eV, phosphorescence from the host material constituting the second light emitting layer 15b occurs. Electron transfer to the luminescent material occurs.
  • the gap between the HOMO level and the LUMO level of the host material itself It is possible to reduce the voltage of the device itself.
  • a host material having a T 1 larger than T 1 of the phosphorescent light emitting material used for the light emitting layer 15 for the second light emitting layer 15b it is preferable to use a host material having a T 1 larger than T 1 of the phosphorescent light emitting material used for the light emitting layer 15 for the second light emitting layer 15b. Even when the host material has T 1 smaller than T 1 of the phosphorescent material, if the difference is about 0.1 eV, transfer of excitation energy from the phosphorescent material hardly occurs. Therefore, any host material having a T 1 smaller by about 0.1 eV than the T 1 of the phosphorescent material can be applied.
  • TmTyPB 1,3,5-tri (m-pyrid-3-yl-phenyl) benzene
  • TmTyPB 1,3,5-tri (m-pyrid-3-yl-
  • the electron transport material used for the electron transport layer of the organic EL element using the conventional blue phosphorescent light-emitting material is used. There is no problem.
  • the host materials applicable to the first light emitting layer 15a and the second light emitting layer 15b have been described above, but are not necessarily limited to the above host materials.
  • an appropriate host material satisfying the above-described conditions may be selected and used for each light emitting layer. That is, any host material that satisfies the above-described conditions is not limited to the host materials listed above. Therefore, the host material to be used may be determined in consideration of the combination of the host materials used for each layer of the organic EL element 11 and the phosphorescent material used for the organic EL element 11. Further, the host materials to be used are not limited to two types, but at least two types, that is, a plurality of host materials may be used.
  • the hole injecting material that can be used for the hole injecting layer 13 is not particularly limited, and for example, a known hole injecting material can be used.
  • a known hole injecting material can be used.
  • a known hole injecting material can be used.
  • a known hole injecting material can be used.
  • a known hole injecting material can be used.
  • a known hole injecting material can be used.
  • a known hole injecting material can be used.
  • a known hole injecting material can be used.
  • a known hole injecting material can be used.
  • a known hole injecting material can be used.
  • a known hole injecting material can be used.
  • a known hole injecting material can be used.
  • DPAS 9,10-diphenylanthracene-2-sulfonate
  • the hole transporting material that can be used for the hole transporting layer 14 is not particularly limited, and for example, a known hole transporting material can be used.
  • a known hole transporting material can be used.
  • TAPC, DPAS, DNTPD, Ir (dpbic) 3 , TCTA, BTPD, DTASi, or a host material used for the first light emitting layer 15a can be applied.
  • the electron transporting material that can be used for the electron transporting layer 16 is not particularly limited, and for example, a known electron transporting material can be used.
  • a known electron transporting material can be used.
  • BCP 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline
  • TPBI 1,3,5-tris
  • TPBI 1,3,5-tris
  • TTZ 3-phenyl -4 (1′-naphthyl) -5-phenyl-1,2,4-triazole (TAZ), 4,7-diphenyl-1,10-phenanthroline (Bphen)
  • Ad-Cz dipalmitoylphosphatidylserine (DPPS) 1,3,5-tri (m-pyrid-3-yl-phenyl) benzene (TmPyPB), 1,3,5-tri (p-pyrid-3-yl-phenyl) benzene (TpPyPB), or A host material or the like used for the
  • the electron injecting material that can be used for the electron injecting layer 17 is not particularly limited, and for example, a known electron injecting material can be used.
  • a known electron injecting material can be used.
  • LiF, BCP, TPBI, TAZ, Bphen, Ad-Cz, DPPS, TmPyPB, TpPyPB, or a host material used for the second light emitting layer 15b can be applied.
  • the manufacturing process of the organic EL element 11 will be briefly described. As described above, the organic EL element usually has a transistor as a switching element, but the manufacturing process is not mentioned in this embodiment.
  • the anode 12 is patterned on each transistor (anode forming step). Then, each layer of the organic layer is formed on the formed anode 12.
  • an organic insulating film (not shown) may be provided around the anode 12.
  • the organic insulating film it is preferable to use a polyimide-based resin material or the like.
  • the organic insulating film is not particularly limited thereto, and for example, a known organic insulating material can be used.
  • the hole injection layer 13 is formed (hole injection layer forming step).
  • a hole injecting material is deposited on the anode 12.
  • the thickness of the hole injection layer 13 is preferably about 45 nm. In this way, the hole injection layer 13 is formed.
  • the hole transport layer 14 is formed (hole transport layer forming step).
  • a hole transporting material is deposited on the hole injection layer 13.
  • the thickness of the hole transport layer 14 is preferably about 15 nm. In this way, the hole transport layer 14 is formed.
  • the light emitting layer 15 is formed. Specifically, a host material for the first light emitting layer 15a and a phosphorescent light emitting material are co-evaporated on the hole transport layer 14 (first light emitting layer forming step). At this time, the host material is preferably doped with about 7.5% of a phosphorescent material. In this way, the first light emitting layer 15a is formed. Note that the thickness of the layer is preferably about 10 nm.
  • the host material for the second light emitting layer 15b and the phosphorescent light emitting material are co-evaporated on the first light emitting layer 15a (second light emitting layer forming step).
  • the host material is preferably doped with about 7.5% of a phosphorescent material.
  • the second light emitting layer 15b is formed.
  • the thickness of the layer is preferably about 10 nm.
  • the electron transport layer 16 is formed (electron transport layer forming step).
  • An electron transporting material is deposited on the light emitting layer 15.
  • the thickness of the electron transport layer 16 is preferably about 30 nm. In this way, the electron transport layer 16 is formed.
  • the electron injection layer 17 is formed (electron injection layer forming step).
  • An electron injecting material is deposited on the electron transport layer 16. In this way, the electron injection layer 17 is formed.
  • a cathode is formed (cathode formation step).
  • a cathode is patterned on the electron injection layer 17 to complete the organic EL element 11.
  • an electron transporting material may be used as the host material of the second light emitting layer 15b, and the second light emitting layer 15b may also serve as the electron transport layer 16.
  • summary of the organic EL element in which a 1st light emitting layer serves as a positive hole transport layer, and a 2nd light emitting layer serves as an electron transport layer is demonstrated.
  • the first embodiment is the same as the first embodiment except that the first light emitting layer also serves as a hole transport layer and the second light emitting layer also serves as an electron transport layer.
  • the organic EL element according to this embodiment has an organic layer between an anode and a cathode formed on a substrate.
  • the said organic layer forms a hole injection layer, a light emitting layer, and an electron injection layer in order.
  • the light emitting layer has a two-layer structure, and includes a first light emitting layer and a second light emitting layer.
  • the organic EL device according to this embodiment is configured such that the gap between the highest occupied level (HOMO level) and the lowest vacant level (LUMO level) of the host material constituting the light emitting layer is reduced. . Thereby, the probability that the hole and electron in a light emitting layer recombine can be raised, keeping the mobility of the hole and electron in an organic layer high. This will be described in detail below.
  • an organic EL element usually has a transistor (not shown) such as an organic thin film transistor substrate as a switching element, detailed description thereof is not mentioned in the present embodiment.
  • FIG. 3 is a diagram showing an energy diagram of each layer constituting the organic EL element 21.
  • the organic layer of the organic EL element 21 is formed by sequentially forming the hole injection layer 23, the light emitting layer 25, and the electron injection layer 27.
  • the light emitting layer 25 has a two-layer structure, and includes a first light emitting layer 25a and a second light emitting layer 25b.
  • the first light emitting layer 25a and the second light emitting layer 25b are doped with a single phosphorescent material.
  • the holes injected from the anode 22 are received from the hole injecting layer 23 and propagate to the vicinity of the interface with the second light emitting layer 25b.
  • the electrons injected from the cathode 30 are received from the electron injection layer 27 and propagate to the vicinity of the interface with the first light emitting layer 25a.
  • the holes propagated from the first light emitting layer 25a and the electrons propagated from the second light emitting layer 25b recombine, thereby emitting light. To do.
  • the organic layer host material is selected in the same manner as in the first embodiment. Specifically, as shown in FIG. 3, the host material constituting the first light emitting layer 25a has a LUMO level 29 of the phosphorescent light emitting material and a LUMO level of the host material constituting the second light emitting layer 25b.
  • the host material constituting the first light emitting layer 25a has a LUMO level 29 of the phosphorescent light emitting material and a LUMO level of the host material constituting the second light emitting layer 25b.
  • the host material constituting the second light emitting layer 25b includes a material having a HOMO level deeper than the HOMO level 28 of the phosphorescent light emitting material and the HOMO level of the host material constituting the first light emitting layer 25a (
  • the holes propagated to the first light emitting layer 25a can be blocked from moving to the second light emitting layer 25b, and the electrons propagated to the second light emitting layer 25b enter the first light emitting layer 25a. Can be blocked from moving. Accordingly, it is possible to reduce the number of holes that move to the second light emitting layer 25b without recombining with electrons, and the number of electrons that move to the first light emitting layer 25a without recombining with holes. As a result, the probability that holes and electrons recombine can be increased. Therefore, in the organic EL element 21 according to the present embodiment, the probability that holes and electrons are recombined in the light emitting layer 25 can be increased, so that the internal quantum yield can be improved and the light emission efficiency can be improved.
  • the layer structure of the organic EL element 21 can be simplified according to the present embodiment. it can. Therefore, the manufacturing process of the organic EL element 21 can be simplified. Moreover, since each injection layer and each transport layer can be omitted, the production cost of the organic EL element 21 can be kept low.
  • the first light emitting layer 25a also serves as a hole transport layer
  • the second light emitting layer 25b also serves as an electron transport layer. Therefore, in order to improve hole injection in the hole injection layer 23, the hole injection layer 23 may be doped with a p-dopant. Similarly, in order to improve electron injection in the electron injection layer 27, the electron injection layer 27 may be doped with an n-dopant. According to this, injection of holes in the hole injection layer is promoted, and injection of electrons in the electron injection layer is promoted. Thus, holes and electrons can be sufficiently propagated to the light emitting layer.
  • a region formed only of the host material may be provided between the light emitting layer 25 and the hole injection layer 23.
  • This region functions as an electron blocking layer and can prevent energy deactivation due to exciplex at the interface between the light emitting layer 25 and the hole injection layer 23. That is, energy loss from the light emitting layer 25 to the hole injection layer 23 can be prevented.
  • a region formed only of the host material as a hole blocking layer may be provided between the light emitting layer 25 and the electron injection layer 27.
  • the thickness of each layer is about 10 nm.
  • a host material constituting the first light emitting layer 25a may be used.
  • a host material constituting the electron injection layer 27 may be used. According to this, the manufacturing process of the organic EL element 21 can be further simplified. Moreover, since the material used for the organic EL element 21 can be reduced, the manufacturing cost of the organic EL element 21 can be further reduced.
  • the manufacturing process of the organic EL element 21 will be briefly described. As described above, the organic EL element usually has a transistor as a switching element, but the manufacturing process is not mentioned in this embodiment.
  • the process until the anode 22 is formed on the substrate is the same as the process of the first embodiment, and is omitted here.
  • the process of forming an organic material on the anode 22 will be described.
  • the hole injection layer 23 is formed. Specifically, a hole injecting material and a p-dopant are co-evaporated on the anode 22. At this time, it is preferable to dope about 10% of p-dopant into the hole injecting material. In this way, the hole injection layer 23 is formed.
  • the layer thickness is preferably about 50 nm.
  • the host material for the first light emitting layer 25a and the phosphorescent light emitting material are co-evaporated on the hole injection layer 23 (first light emitting layer forming step).
  • the host material is preferably doped with about 7.5% of a phosphorescent material.
  • the first light emitting layer 25a is formed.
  • the thickness of the layer is preferably about 10 nm.
  • a host material for the second light emitting layer 25b and a phosphorescent light emitting material are co-evaporated on the first light emitting layer 25a (second light emitting layer forming step).
  • the host material is preferably doped with about 7.5% of a phosphorescent material.
  • the first light emitting layer 25b is formed.
  • the thickness of the layer is preferably about 10 nm.
  • the electron injection layer 27 is formed (electron injection layer forming step).
  • An electron injecting material and an n-dopant are deposited on the light emitting layer 25.
  • the electron injection layer 27 is formed.
  • the thickness of the layer is preferably about 30 nm.
  • the cathode 30 is formed (cathode forming step).
  • the cathode 30 is patterned on the electron injection layer 27, and the organic EL element 21 is completed.
  • the hole injection layer 23 and the electron injection layer 27 are doped with dopants.
  • the hole injection layer 13 and the electron injection layer 17 are respectively formed.
  • a dopant may be doped.
  • the hole transport layer 14 and the electron transport layer 16 are doped with dopants for the purpose of promoting the transport of holes and electrons, respectively.
  • FIG. 4 is a diagram schematically illustrating an organic EL display device 40 including the organic EL elements 11 and 21.
  • an organic EL display device 40 including organic EL elements 11 and 21 has a pixel unit 7, a gate signal side driving circuit 5, a data signal side driving circuit 6, a wiring 3, a current on a substrate 20. It has a supply line 4, a sealing substrate 42, an FPC (Flexible Printed Circuits) 2, and an external drive circuit 1.
  • a pixel unit 7 As shown in FIG. 4, an organic EL display device 40 including organic EL elements 11 and 21 has a pixel unit 7, a gate signal side driving circuit 5, a data signal side driving circuit 6, a wiring 3, a current on a substrate 20. It has a supply line 4, a sealing substrate 42, an FPC (Flexible Printed Circuits) 2, and an external drive circuit 1.
  • FPC Flexible Printed Circuits
  • the external driving circuit 27 sequentially selects the scanning lines (scanning lines) of the pixel unit 7 by the gate signal side driving circuit 5, and for each pixel element arranged along the selected scanning line, on the data signal side.
  • the pixel data is written in the drive circuit 6. That is, when the gate signal side driving circuit 5 sequentially drives the scanning lines and the data signal side driving circuit 6 outputs the pixel data to the data lines, the driven scanning lines and the data lines to which the data is output intersect.
  • the pixel element arranged at the position to be driven is driven.
  • FIG. 5 is a diagram showing an outline of a mobile phone 70 having an organic EL display device.
  • FIG. 6 is a diagram showing an outline of a television receiver 80 provided with an organic EL display device.
  • an organic EL display device including the organic EL elements 11 and 21 according to the present embodiment can be mounted on the display unit 59 of the mobile phone 70.
  • 55 is an audio input unit
  • 56 is an audio output unit
  • 57 is a main body part
  • 58 is an antenna
  • 60 is an operation switch. Since these members have functions similar to those of a conventional mobile phone, description thereof is omitted here. Further, the specific configuration of the mobile phone 70 is not mentioned here.
  • an organic EL display device including the organic EL element 1 according to this embodiment can be mounted on the display unit 61 of the television receiver 80.
  • 62 shown in the figure is a speaker. Since the television receiver 80 has the same configuration as that of the conventional television receiver 80 except that the display unit 61 includes the organic EL display device according to the present embodiment, a specific configuration is provided. Is not mentioned here.
  • an organic EL display device with high luminous efficiency can be realized, and the organic EL display device can be used in various electronic devices including a display unit. It can be installed.
  • the organic EL display device having the display unit including the organic EL elements 11 and 21 according to the present embodiment has been described.
  • the organic EL elements 11 and 21 can also be used as a light source of a lighting device. It is. A specific example is shown in FIG. FIG. 7 is a diagram showing an outline of a lighting device 90 including the organic EL elements 11 and 21.
  • the illumination device 90 including the organic EL element 1 includes an optical film 71, a substrate 11, an anode 2, an organic EL layer 10, a cathode 9, a heat diffusion sheet 64, a sealing substrate 65, and a sealing resin. 63, a heat radiation member 66, a driving circuit 67, a wiring 68, and a hook ceiling 69.
  • the organic EL element 1 As described above, by providing the organic EL element 1 according to this embodiment, it is possible to provide a lighting device with high luminous efficiency.
  • the highest occupied level (HOMO) and the lowest empty level of each of the first host material, the second host material, and the organic light emitting material are further provided.
  • the position (LUMO) satisfies the following relational expressions (3) and (4).
  • the light emitting layer further includes a first light emitting layer formed on the anode side and a second light emitting layer formed on the cathode side,
  • the host material constituting the first light emitting layer has the lowest vacancy level of the host material constituting the second luminescent layer, and the lowest vacancy level shallower than the lowest vacant level of the organic light emitting material.
  • the host material constituting the two light emitting layers has the highest occupied level of the host material constituting the first light emitting layer and the highest occupied level deeper than the highest occupied level of the organic light emitting material. It is characterized by being.
  • the host material constituting the first light emitting layer includes the lowest vacant level (
  • ) are used.
  • the host material constituting the second light emitting layer includes an organic light emitting material and a highest occupied level deeper than the host material constituting the first light emitting layer (
  • ) is used. According to this, since the highest occupied level of the host material constituting the second light emitting layer is deeper than the highest occupied level of the host material and the organic light emitting material constituting the first light emitting layer, the first light emitting layer Can be prevented from moving to the second light emitting layer.
  • the lowest vacancy level of the host material constituting the first light emitting layer is shallower than the lowest vacant level of the host material and organic light emitting material constituting the second light emitting layer, it was propagated to the second light emitting layer. Electrons can be blocked from moving to the first light emitting layer. Thus, light is emitted by recombination of holes and electrons propagated to the organic light emitting material at the interface between the first light emitting layer and the second light emitting layer.
  • the organic EL device As described above, in the organic EL device according to the present invention, it is possible to reduce the number of holes that move to the second light emitting layer without recombining with electrons, and the number of electrons that move to the first light emitting layer without recombining with holes. It becomes. As a result, since the probability that holes and electrons recombine can be increased, the drive voltage of the organic EL element can be lowered. In addition, since the probability of recombination of holes and electrons in the light emitting layer is increased, the internal quantum yield is improved, and the light emission efficiency can be improved.
  • the highest occupied level (HOMO) and the lowest vacant level (LUMO) of each of the first host material, the second host material, and the organic light emitting material are further included. ) Satisfies the following relational expressions (5) to (8).
  • the highest occupied level (HOMO) and the lowest vacant level (LUMO) of each of the first host material, the second host material, and the organic light emitting material are further included. ) Is characterized by satisfying at least one of the following relational expressions (9) and (10).
  • the presence of electrons in the organic light-emitting material can prevent the electrons from moving to an anode-side material such as a hole transport material.
  • the presence of holes in the organic light emitting material can prevent the holes from moving to the cathode side material such as the electron transport material.
  • the host material which comprises said 1st light emitting layer, and the host material which comprises said 2nd light emitting layer are higher than the excitation triplet level of the said organic light emitting material. It is characterized by having an excited triplet level.
  • excitation energy can be confined in the organic light emitting material in the light emitting layer, and movement of excitation energy from the organic light emitting material can be prevented.
  • the organic layer includes a hole injection layer doped with a dopant that promotes injection of holes from the anode to the organic layer, and the organic layer from the cathode. And an electron injection layer doped with a dopant that promotes electron injection into the substrate.
  • the injection of carriers injected from the first electrode into the organic layer is promoted, and the injection of carriers injected from the second electrode into the organic layer is promoted.
  • holes and electrons can be sufficiently propagated to the light emitting layer.
  • the organic electroluminescence device according to the present invention is characterized in that there is a region not doped with the dopant and the organic light emitting material between the hole injection layer and the light emitting layer.
  • the organic electroluminescence device according to the present invention is characterized in that there is a region not doped with the dopant and the organic light emitting material between the electron injection layer and the light emitting layer.
  • the region not doped with the organic light emitting material and the dopant between the light emitting layer and the first carrier injection layer functions as a carrier blocking layer.
  • the region where the organic light emitting material and the dopant are not doped between the light emitting layer and the second carrier injection layer can also prevent energy loss from the light emitting layer to the second carrier injection layer.
  • the organic light emitting material is a phosphorescent light emitting material.
  • Example 1 A silicon semiconductor film was formed on a glass substrate by a plasma chemical vapor deposition (plasma CVD) method, subjected to crystallization treatment, and then a polycrystalline semiconductor film was formed. Subsequently, the polycrystalline silicon thin film was etched to form a plurality of island patterns. Next, silicon nitride (SiN) was formed as a gate insulating film on each island of the polycrystalline silicon thin film. Thereafter, a laminated film of titanium (Ti) -aluminum (Al) -titanium (Ti) was sequentially formed as a gate electrode, and patterned by an etching process. On the gate electrode, a source electrode and a drain electrode were formed using Ti—Al—Ti to manufacture a plurality of thin film transistors.
  • plasma CVD plasma chemical vapor deposition
  • ITO indium tin oxide
  • N, N-dicarbazoyl-3,5-benzene was deposited on the hole injection layer at a deposition rate of 1 cm / sec by vacuum deposition. In this way, a 15 nm-thick hole transport layer was formed on the hole injection layer.
  • (tris (2,4,6-trimethyl-3-yl) -3- (pyridin-3-yl) phenyl) borane (3TPYMB) and FIr6 are co-coated on the first light-emitting layer by vacuum deposition. Vapor deposited. At this time, doping was performed such that about 7.5% of FIr6 was contained in 3TPYMB. Thus, the 10-nm-thick 2nd light emitting layer was formed on the 1st light emitting layer.
  • TPBI 1,3,5-tris (N-phenylbenzimidazol-2-yl) benzene
  • LiF was deposited on the electron transport layer by a vacuum deposition method at a deposition rate of 1 cm / sec to form a LiF film having a thickness of 0.5 nm. Thereafter, an Al film having a thickness of 100 nm was formed on the LiF film using Al. In this way, a laminated film of LiF and Al was formed as a cathode, and an organic EL element was produced.
  • the current efficiency and lifetime T 50 at 1000 cd / m 2 of the obtained organic L device were measured. As a result, the current efficiency was 28 cd / A, and the lifetime T 50 was a good value of 5000 h.
  • Example 2 Since the steps until the anode is formed are the same as those in Example 1, they are omitted here. Below, it demonstrates from the process of forming a positive hole injection layer.
  • 4CzPBP and tetrafluorotetracyanoquinodimethane (TCNQF 4 ) were co-deposited at a deposition rate of 1 ⁇ / sec by a vacuum deposition method. At this time, doping was performed so that about 10% of TCNQF 4 was contained in 4CzPBP. In this way, a hole injection layer having a thickness of 50 nm was formed on the anode.
  • 4 CzPBP was deposited on the hole injection layer by 10 nm, and then 4 CzPBP and FIr6 were co-deposited by a vacuum deposition method. At this time, doping was performed so that FIr6 was included in about 4% in 4CzPBP. In this way, a first light emitting layer having a thickness of 10 nm was formed.
  • 3TPYMB and FIr6 were co-deposited on the first light emitting layer by a vacuum deposition method. At this time, doping was performed such that about 7.5% of FIr6 was contained in 3TPYMB. Thus, the 10-nm-thick 2nd light emitting layer was formed on the 1st light emitting layer.
  • 3TPYMB and cesium carbonate (Cs 2 CO 3 ) were co-deposited on the second light emitting layer by a vacuum evaporation method. At this time, doping was performed so that about 50% of Cs 2 CO 3 was contained in 3TPYMB. In this way, an electron injection layer having a thickness of 30 nm was formed on the second light emitting layer.
  • LiF was deposited on the electron injection layer by a vacuum deposition method at a deposition rate of 1 cm / sec to form a LiF film having a thickness of 0.5 nm. Thereafter, an Al film having a thickness of 100 nm was formed on the LiF film using Al. In this way, a laminated film of LiF and Al was formed as a cathode, and an organic EL element was produced.
  • the current efficiency and lifetime T 50 at 1000 cd / m 2 of the obtained organic EL element were measured. As a result, the current efficiency was 25 cd / A, and the lifetime T 50 was a good value of 4000 h.
  • the light emitting layer has a multi-layer structure, and a material considering a phosphorescent light emitting material is used as the host material of the light emitting layer.
  • a material considering a phosphorescent light emitting material is used as the host material of the light emitting layer.
  • 4CzPBP having a LUMO level shallower than the LUMO level of FIr6 and the host material (3TPYMB) of the second light emitting layer is used as the host material of the first light emitting layer.
  • 3TPYMB having a HOMO level deeper than the HOMO level of the host material (4CzPBP) of FIr6 and the first light-emitting layer is used as the host material of the second light-emitting layer.
  • 3TPYMB has a LUMO level deeper than FIr6, and 4CzPBP has a HOMO level shallower than FIr6. Accordingly, it is possible to prevent holes injected from the anode from moving to the second light emitting layer. Similarly, it is possible to prevent electrons injected from the cathode from moving to the first light emitting layer. This makes it possible to reduce the number of holes that move to the second light emitting layer without recombining with electrons, and to reduce the number of electrons that move to the first light emitting layer without recombining with holes. As a result, the probability that holes and electrons recombine can be increased. Therefore, the organic EL device according to the first embodiment exhibited both good values current efficiency and lifetime T 50.
  • the first light-emitting layer also serves as the hole transport layer
  • the second light-emitting layer also serves as the electron transport layer.
  • the hole injection layer and the electron injection layer are each doped with a dopant. ing. Therefore, the injection of holes in the hole injection layer is promoted, and the injection of electrons in the electron injection layer is promoted. Thus, holes and electrons can be sufficiently propagated to the light emitting layer.
  • Example 2 since the same host material as in Example 1 is used, the number of holes that move to the second light emitting layer without recombination with electrons is reduced, and the first light emitting layer without recombination with holes. It is possible to reduce the number of electrons that move to. As a result, the probability that holes and electrons recombine can be increased. Therefore, in the organic EL device according to this Example 2 exhibited both good values current efficiency and lifetime T 50.
  • the current efficiency and driving voltage at 1000 cd / m 2 of the obtained organic EL element were measured.
  • the current efficiency was 24 cd / A, and the voltage was about 80% that of Example 1, indicating a good value. Therefore, it is experimentally found that high efficiency can be expected if the difference between the HOMO level of the host material of the first light emitting layer and the HOMO level of the phosphorescent light emitting material is between 0.1 and 0.3 eV. It was.
  • the HOMO level of the host material constituting the first light emitting layer is preferably shallower than the HOMO level of the phosphorescent light emitting material.
  • the difference between the HOMO level of the host material constituting the first light emitting layer and the HOMO level of the phosphorescent light emitting material is larger than 0.5 eV, the probability that holes can be thermally excited is lowered. End up. Therefore, it can be said that the difference between the HOMO level of the host material constituting the first light emitting layer and the HOMO level of the phosphorescent light emitting material is preferably within 0.5 eV.
  • the electron (hole) moving speed can be expressed by a general Arrhenius equation as in the following equation (1).
  • k ET is an electron (hole) transfer rate constant
  • A is a frequency factor (a constant independent of temperature).
  • k ET Aexp ( ⁇ E / RT) (1)
  • A is 10 11 M ⁇ 1 s ⁇ 1 in the case of an intermolecular reaction.
  • the result of calculating the value of the rate constant by the numerical value of ⁇ E from the formula (1) is shown below.
  • the energy [f (x)] stabilized by the electric field can be expressed as the following formula (2). Specifically, it is energy that stabilizes electrons at a position of distance x when an electric field of V is applied. Note that q is an elementary charge (an absolute value of an electron charge).
  • the difference between the HOMO level of the host material constituting the first light emitting layer and the HOMO level of the phosphorescent light emitting material is within 0.5 eV, the probability that the holes are thermally excited increases. And the probability that electrons recombine can be increased. Further, if the difference between the HOMO level of the host material constituting the first light emitting layer and the HOMO level of the phosphorescent light emitting material is larger than 0 eV, the gap between the HOMO level and the LUMO level of the host material itself is narrowed. Thus, the voltage of the device itself can be reduced.
  • the LUMO level of the host material constituting the second light emitting layer is preferably shallower than the LUMO level of the phosphorescent light emitting material, and the difference is larger than 0 eV and within 0.5 eV. It is preferable.
  • the LUMO level of the host material of the first light emitting layer is shallower than the LUMO level of the phosphorescent light emitting material, the difference is larger than 0.5 eV, and it can be driven at a low voltage within 0.7 eV. I was able to confirm. That is, 0.5 eV ⁇ (
  • the HOMO level of the host material constituting the second light emitting layer is deeper than the HOMO level of the phosphorescent light emitting material, and the difference is larger than 0.5 eV and is driven at a low voltage if it is within 0.7 eV. It was confirmed experimentally that it was possible. That is, 0.5 eV ⁇ (
  • the present invention can be used for various devices using organic EL elements, and can be used for display devices such as televisions.

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Abstract

La présente invention concerne un élément électroluminescent organique (11) ayant une couche électroluminescente (15) d'une structure à deux couches. Une première couche électroluminescente (15a) est composée d'un matériau hôte ayant un niveau LUMO inférieur à un niveau LUMO (19) d'un matériau électroluminescent à phosphorescence et un niveau LUMO d'un matériau hôte dont est composé une seconde couche électroluminescente (15b) (|LUMO (matériau hôte de la première couche électroluminescente) | < |LUMO (matériau hôte de la seconde couche électroluminescente et |LUMO (matériau hôte de la première couche électroluminescente | < |LUMO (matériau électroluminescent à phosphorescence)|). Une seconde couche électroluminescente (15b) est composée d'un matériau hôte ayant un niveau HOMO qui est supérieur à un niveau HOMO (18) du matériau électroluminescent à phosphorescence et un niveau HOMO du matériau hôte dont est composé la première couche électroluminescente (15a) (|HOMO (matériau hôte de la seconde couche électroluminescente)| > |HOMO (matériau hôte de la première couche électroluminescente)| et |HOMO (matériau hôte de la seconde couche électroluminescente) | > |HOMO (matériau électroluminescent à phosphorescence)|). Avec cette structure, il est possible de bloquer le mouvement des trous vers la seconde couche électroluminescente (15b) et de bloquer le mouvement des trous vers la première couche électroluminescente (15a). En conséquence, une probabilité de réassociation des trous et des électrons les uns avec les autres est augmentée et une tension d'attaque de l'élément électroluminescent organique (11) est réduite, ce qui permet d'améliorer l'efficacité de l'émission lumineuse.
PCT/JP2010/067883 2009-11-27 2010-10-12 Élément électroluminescent organique, son procédé de fabrication et dispositif d'affichage par électroluminescence organique WO2011065137A1 (fr)

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